1. Field of the Invention
The present invention relates generally to the production of semiconductor products. More particularly, the invention relates to a method of filling trenches, holes and other surface discontinuities in semiconductor products. The invention also relates to an apparatus for forcing conductive metal into openings in semiconductor products.
2. Discussion of the Related Art
A method of filling metal into openings in semiconductor products is described in U.S. Pat. No. 5,527,561 (Dobson). According to the Dobson process, via holes are formed in a semiconductor wafer. An aluminum layer is formed over the holes by sputtering. The aluminum layer is deformed and caused to flow into the holes by high pressure and high temperature. The high pressure is applied by pressurized gas.
The Dobson process has several disadvantages. First, it may not always fill the via holes as desired. The process will not work unless the holes are completely covered over by aluminum. That is, the process will not work if openings in the aluminum layer permit equalization of the pressures inside and outside the holes. Openings in the aluminum layer may be formed during the sputtering process or during the application of high pressure and high temperature.
Another problem with the Dobson process is that it would be difficult to operate efficiently. It takes time to pressurize the gas in the Dobson process. The time it takes to handle the pressurized gas reduces the rate at which wafers can be processed. In addition, the mechanisms that would be used to create and maintain the high pressure are relatively large and complicated.